01Trigger engine core

<main class="stage">
  <section class="te is-demo" id="te" aria-label="Scroll trigger engine">
    <header class="te__head">
      <p class="te__title">Trigger engine</p>
      <p class="te__attr"><code>data-scroll="up"</code></p>
    </header>
    <div class="te__view" id="te-view" tabindex="0" role="region" aria-label="Section list — scroll and they appear in order">
      <div class="te__track">
        <article class="te__card" data-scroll="up" data-threshold="0.4" data-once="true"><b>01</b><span>rises from below</span></article>
        <article class="te__card" data-scroll="left" data-threshold="0.4" data-once="true"><b>02</b><span>slides in from the left</span></article>
        <article class="te__card" data-scroll="right" data-threshold="0.4" data-once="true"><b>03</b><span>slides in from the right</span></article>
        <article class="te__card" data-scroll="zoom" data-threshold="0.4" data-once="true"><b>04</b><span>starts small, then grows</span></article>
      </div>
    </div>
    <footer class="te__foot">
      <span class="te__dot" aria-hidden="true"></span>
      <span class="te__state">when it enters the screen <b>is-visible</b></span>
    </footer>
  </section>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 트리거 엔진 코어 — 네 방향 진입을 하나의 관찰자 설정으로 재생한다
// 미리보기(.is-demo)는 CSS 키프레임이 스크롤을 대신하고, 손이 닿으면 JS 가 IntersectionObserver 를 붙인다
$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-blue;

@include stage($stage-paper);

.te {
  position: relative;
  box-sizing: border-box;
  width: min(320px, 92vw);
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
  box-shadow: $shadow-raised;
}

.te__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: $sp-2;
  padding: $sp-2 $sp-3;
}
.te__title {
  margin: 0;
  font-size: 13px;
  font-weight: 800;
  line-height: 1.3;
}
.te__attr {
  margin: 0;
  font-size: 10px;
  line-height: 1.3;
  color: rgba($subject-ink, .72);
  code { font-family: "Consolas", "Menlo", monospace; }
}

.te__view {
  height: 100px;
  overflow-y: auto;
  padding: 0 $sp-3;
  outline: none;
}
.te__track {
  display: grid;
  gap: $sp-2;
  padding-bottom: 140px;
}

.te__card {
  display: flex;
  align-items: center;
  gap: $sp-2;
  box-sizing: border-box;
  padding: $sp-4;
  border-radius: $r-control;
  background: $subject-blue-deep;
  color: $subject-cream;
  opacity: 0;
  transition: opacity $dur-enter $easing, transform $dur-enter $easing;

  b { font-size: 20px; font-weight: 800; line-height: 1; }
  span { font-size: 12px; font-weight: 700; line-height: 1.3; }
}
.te__card[data-scroll="up"] { transform: translateY(18px); }
.te__card[data-scroll="left"] { transform: translateX(-24px); }
.te__card[data-scroll="right"] { transform: translateX(24px); }
// 카드는 스스로 완결한 요소라 중심에서 커진다 (기본 origin 유지)
.te__card[data-scroll="zoom"] { transform: scale(.82); }

.te__card.is-visible {
  opacity: 1;
  transform: none;
}

.te__foot {
  display: flex;
  align-items: center;
  gap: $sp-2;
  padding: $sp-2 $sp-3;
  border-top: 1px solid rgba($subject-ink, .12);
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
  b { color: $subject-orange-deep; }
}
.te__dot {
  width: 8px;
  height: 8px;
  border-radius: $r-pill;
  background: $color;
}

// 미리보기 — 스크롤 대신 트랙을 밀어 올리고 카드가 순서대로 들어오는 것처럼 보인다
.te.is-demo {
  .te__track {
    animation-name: te-flow;
    animation-duration: $duration;
    animation-timing-function: $easing;
    animation-iteration-count: infinite;
    animation-fill-mode: backwards;
  }
  // 나타남은 한 프레임 컷(te-show), 이동은 이징(te-rise) — 페이드 중간 프레임이 유령으로 찍히지 않는다
  .te__card {
    animation-name: te-show, te-rise;
    animation-duration: $duration, $duration;
    animation-timing-function: steps(1, end), $easing;
    animation-iteration-count: infinite, infinite;
    animation-fill-mode: backwards, backwards;
  }
  .te__card:nth-child(1) { animation-delay: 0s, 0s; }
  .te__card:nth-child(2) { animation-delay: $duration * .12, $duration * .12; }
  .te__card:nth-child(3) { animation-delay: $duration * .24, $duration * .24; }
  .te__card:nth-child(4) { animation-delay: $duration * .36, $duration * .36; }
  .te__dot {
    animation-name: te-blink;
    animation-duration: $duration;
    animation-timing-function: steps(1, end);
    animation-iteration-count: infinite;
  }
}

@keyframes te-flow {
  0%, 8% { transform: translateY(0); }
  46%, 54% { transform: translateY(-80px); }
  88%, 100% { transform: translateY(-160px); }
}
@keyframes te-show {
  0% { opacity: 0; }
  4%, 92% { opacity: 1; }
  96% { opacity: 0; }
}
@keyframes te-rise {
  0% { transform: translateY(18px); }
  28%, 92% { transform: none; }
  100% { transform: translateY(18px); }
}
@keyframes te-blink {
  0% { background: rgba($subject-ink, .2); }
  24% { background: $color; }
  90% { background: rgba($subject-ink, .2); }
}

// 320×200 무대는 세로 여유가 거의 없다 — 목록 칸을 줄여 머리·바닥과 함께 화면 안에 넣는다
@media (max-width: 340px) {
  .te { width: 100%; }
  .te__view { height: 72px; }
  .te__card { padding: $sp-2; }
  .te__card b { font-size: 16px; }
  .te__card span { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .te__card { transition: none !important; }
  .te.is-demo .te__track,
  .te.is-demo .te__card,
  .te.is-demo .te__dot { animation: none !important; }
  // 정지 상태 — 카드가 전부 보인다
  .te.is-demo .te__card { opacity: 1 !important; transform: none !important; }
  .te.is-demo .te__dot { background: $color !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.te {
  position: relative;
  box-sizing: border-box;
  width: min(320px, 92vw);
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.te__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  padding: 8px 12px;
}

.te__title {
  margin: 0;
  font-size: 13px;
  font-weight: 800;
  line-height: 1.3;
}

.te__attr {
  margin: 0;
  font-size: 10px;
  line-height: 1.3;
  color: rgba(23, 20, 26, 0.72);
}
.te__attr code {
  font-family: "Consolas", "Menlo", monospace;
}

.te__view {
  height: 100px;
  overflow-y: auto;
  padding: 0 12px;
  outline: none;
}

.te__track {
  display: grid;
  gap: 8px;
  padding-bottom: 140px;
}

.te__card {
  display: flex;
  align-items: center;
  gap: 8px;
  box-sizing: border-box;
  padding: 16px;
  border-radius: 12px;
  background: #0a4fe8;
  color: #fff7e6;
  opacity: 0;
  transition: opacity 600ms cubic-bezier(0.2, 0.8, 0.2, 1), transform 600ms cubic-bezier(0.2, 0.8, 0.2, 1);
}
.te__card b {
  font-size: 20px;
  font-weight: 800;
  line-height: 1;
}
.te__card span {
  font-size: 12px;
  font-weight: 700;
  line-height: 1.3;
}

.te__card[data-scroll=up] {
  transform: translateY(18px);
}

.te__card[data-scroll=left] {
  transform: translateX(-24px);
}

.te__card[data-scroll=right] {
  transform: translateX(24px);
}

.te__card[data-scroll=zoom] {
  transform: scale(0.82);
}

.te__card.is-visible {
  opacity: 1;
  transform: none;
}

.te__foot {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-top: 1px solid rgba(23, 20, 26, 0.12);
  font-size: 10px;
  font-weight: 700;
  line-height: 1.3;
}
.te__foot b {
  color: #c93000;
}

.te__dot {
  width: 8px;
  height: 8px;
  border-radius: 999px;
  background: #2f6df6;
}

.te.is-demo .te__track {
  animation-name: te-flow;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
  animation-fill-mode: backwards;
}
.te.is-demo .te__card {
  animation-name: te-show, te-rise;
  animation-duration: 2s, 2s;
  animation-timing-function: steps(1, end), cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite, infinite;
  animation-fill-mode: backwards, backwards;
}
.te.is-demo .te__card:nth-child(1) {
  animation-delay: 0s, 0s;
}
.te.is-demo .te__card:nth-child(2) {
  animation-delay: 0.24s, 0.24s;
}
.te.is-demo .te__card:nth-child(3) {
  animation-delay: 0.48s, 0.48s;
}
.te.is-demo .te__card:nth-child(4) {
  animation-delay: 0.72s, 0.72s;
}
.te.is-demo .te__dot {
  animation-name: te-blink;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

@keyframes te-flow {
  0%, 8% {
    transform: translateY(0);
  }
  46%, 54% {
    transform: translateY(-80px);
  }
  88%, 100% {
    transform: translateY(-160px);
  }
}
@keyframes te-show {
  0% {
    opacity: 0;
  }
  4%, 92% {
    opacity: 1;
  }
  96% {
    opacity: 0;
  }
}
@keyframes te-rise {
  0% {
    transform: translateY(18px);
  }
  28%, 92% {
    transform: none;
  }
  100% {
    transform: translateY(18px);
  }
}
@keyframes te-blink {
  0% {
    background: rgba(23, 20, 26, 0.2);
  }
  24% {
    background: #2f6df6;
  }
  90% {
    background: rgba(23, 20, 26, 0.2);
  }
}
@media (max-width: 340px) {
  .te {
    width: 100%;
  }
  .te__view {
    height: 72px;
  }
  .te__card {
    padding: 8px;
  }
  .te__card b {
    font-size: 16px;
  }
  .te__card span {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .te__card {
    transition: none !important;
  }
  .te.is-demo .te__track,
  .te.is-demo .te__card,
  .te.is-demo .te__dot {
    animation: none !important;
  }
  .te.is-demo .te__card {
    opacity: 1 !important;
    transform: none !important;
  }
  .te.is-demo .te__dot {
    background: #2f6df6 !important;
  }
}

// Trigger engine 코어 — data-scroll 속성으로 방향·임계값·한 번만 여부를 HTML 에서 정한다
var root = document.getElementById('te');
var view = document.getElementById('te-view');
var cards = Array.prototype.slice.call(document.querySelectorAll('.te__card'));
var observers = [];
function attach(card) {
  var threshold = parseFloat(card.getAttribute('data-threshold')) || 0;
  var once = card.getAttribute('data-once') === 'true';
  var io = new IntersectionObserver(function (entries) {
    entries.forEach(function (entry) {
      if (entry.isIntersecting) {
        entry.target.classList.add('is-visible');
        if (once) io.unobserve(entry.target);
      } else if (!once) {
        entry.target.classList.remove('is-visible');
      }
    });
  }, { root: view, rootMargin: '0px 0px -8px 0px', threshold: threshold });
  io.observe(card);
  observers.push(io);
}
function start() {
  root.classList.remove('is-demo');
  if (observers.length === 0) cards.forEach(attach);
}
view.addEventListener('scroll', start, { passive: true });
view.addEventListener('pointerdown', start);
view.addEventListener('keydown', function (e) {
  if (e.key === 'ArrowDown' || e.key === 'ArrowUp') start();
});

import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./TriggerEngineCore.module.scss";

export type TriggerEngineCoreProps = {
  title?: string;
  attr?: string;
  state?: string;
  cards?: { dir: "up" | "left" | "right" | "zoom"; label: string }[];
  groupLabel?: string;
  listLabel?: string;
  /** 격자 미리보기용 2초 자동 루프. 사람이 손대면 꺼진다 */
  demo?: boolean;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
// ambient 가 얇아 DOM 요소 타입을 못 쓴다 — 필요한 꼴만 로컬 타입으로 선언
type Box<T> = { current: T };
type KeyEvt = { key: string };

const DEFAULT_CARDS: { dir: "up" | "left" | "right" | "zoom"; label: string }[] = [
  { dir: "up", label: "아래에서 올라오며" },
  { dir: "left", label: "왼쪽에서 밀려오며" },
  { dir: "right", label: "오른쪽에서 밀려오며" },
  { dir: "zoom", label: "작게 있다 커지며" },
];

export default function TriggerEngineCore({
  title = "트리거 엔진",
  attr = 'data-scroll="up"',
  state = "화면에 들어오면",
  cards = DEFAULT_CARDS,
  groupLabel = "스크롤 트리거 엔진",
  listLabel = "섹션 목록 — 스크롤하면 순서대로 등장합니다",
  demo = true,
  duration = 2000,
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#2f6df6",
}: TriggerEngineCoreProps) {
  const [live, setLive] = useState(demo);
  const [seen, setSeen] = useState<number[]>([]);
  const viewRef = useRef<HTMLDivElement>(null) as unknown as Box<HTMLDivElement | null>;
  const cardRefs = useRef<(HTMLElement | null)[]>([]) as unknown as Box<(HTMLElement | null)[]>;

  useEffect(() => {
    if (live) return;
    const root = viewRef.current;
    if (!root) return;
    // 카드마다 관찰자를 하나씩 — 임계값이 항목마다 다를 수 있으므로 공유하지 않는다
    const observers = cardRefs.current.map((el, i) => {
      if (!el) return null;
      const io = new IntersectionObserver(
        (entries) => {
          entries.forEach((entry) => {
            if (entry.isIntersecting) {
              setSeen((prev) => (prev.indexOf(i) === -1 ? prev.concat(i) : prev));
              io.unobserve(entry.target);
            }
          });
        },
        { root, rootMargin: "0px 0px -8px 0px", threshold: 0.4 }
      );
      io.observe(el);
      return io;
    });
    return () => {
      observers.forEach((io) => io && io.disconnect());
    };
  }, [live]);

  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--easing": easing,
    "--color": color,
  };

  return (
    <section
      className={`${styles.te} ${live ? styles.isDemo : ""}`}
      style={vars}
      aria-label={groupLabel}
    >
      <header className={styles.head}>
        <p className={styles.title}>{title}</p>
        <p className={styles.attr}><code>{attr}</code></p>
      </header>
      <div
        className={styles.view}
        ref={viewRef as unknown as Box<HTMLDivElement>}
        onScroll={() => setLive(false)}
        onPointerDown={() => setLive(false)}
        onKeyDown={(e: KeyEvt) => {
          if (e.key === "ArrowDown" || e.key === "ArrowUp") setLive(false);
        }}
        tabIndex={0}
        role="region"
        aria-label={listLabel}
      >
        <div className={styles.track}>
          {cards.map((card, i) => (
            <article
              key={card.dir}
              ref={(el: HTMLElement | null) => {
                cardRefs.current[i] = el;
              }}
              className={`${styles.card} ${styles[card.dir]} ${
                seen.indexOf(i) !== -1 ? styles.isVisible : ""
              }`}
            >
              <b>{String(i + 1).padStart(2, "0")}</b>
              <span>{card.label}</span>
            </article>
          ))}
        </div>
      </div>
      <footer className={styles.foot}>
        <span className={styles.dot} aria-hidden="true" />
        <span className={styles.state}>
          {state} <b>is-visible</b>
        </span>
      </footer>
    </section>
  );
}